Adaptive confidence thresholds in telematics system speech recognition

ABSTRACT

A method of configuring a speech recognition unit in a vehicle. The method includes receiving a noise error from the speech recognition unit responsive to a user voice command and reducing a confidence threshold for an appropriate grammar set responsive to the received noise error.

FIELD OF THE INVENTION

This invention relates generally to a telematics system speechrecognition system. In particular, the invention relates to a method,system and computer usable medium for dynamically adapting theconfidence thresholds for speech recognition in a mobile vehicle.

BACKGROUND OF THE INVENTION

The opportunity to personalize features in a mobile vehicle is everincreasing as the automobile is being transformed into a communicationsand entertainment platform as well as a transportation platform. Manynew American cars will be installed with some type of telematics unit toprovide wireless communication and location-based services. Theseservices may be accessed through interfaces such as voice-recognitioncomputer applications, touch-screen computer displays, computerkeyboards, or a series of buttons on the dashboard or console of avehicle.

Currently, telematics service call centers, in-vehicle compact disk (CD)or digital video display (DVD) media, web portals, and voice-enabledphone portals provide various types of location services, includingdriving directions, stolen vehicle tracking, traffic information,weather reports, restaurant guides, ski reports, road conditioninformation, accident updates, street routing, landmark guides, andbusiness finders.

For example, traffic and driving directions may be accessed through avoice portal that uses incoming number identification to generatelocation information based on the area code or prefix of the phonenumber, or to access location information stored in a user's profileassociated with the phone number. Users may be prompted to enter moredetails through a voice interface.

Speech recognition systems are used within vehicles with telematicsunits for various functions. The speech recognition unit receives,recognizes and generates responses to commands, such as “Call,” “Dial,”“Locate,” and “Generate map.”

Confidence thresholds are preset in the voice-recognition applicationsoftware that is installed in the telematics unit. The confidencethreshold establishes the minimum acceptable confidence that a spokenword or sentence is correlated with a stored vocabulary in the system.The optimum confidence threshold is set after testing utterances frommany people with different dialects under different noise levelconditions to obtain statistically significant threshold levels.Different optimum threshold values may be set for different grammar setsto be applicable uniformly across all noise conditions and dialects. Thegrammar set is associated with a command function and includes all thewords that are likely to be uttered during a speech task related to thatcommand function.

Since the optimum threshold values are statistical, they do not meet theneeds of everyone in different noise conditions. The threshold values,which are sufficient in low noise conditions, are sometimes inadequatein high noise conditions for a user. The threshold values are sometimesinadequate based on the volume of a particular user. In that case, thespeech recognition system is unable, with a confidence greater than thedefault confidence threshold level, to correlate a spoken phrase withthe stored phrases in the speech recognition system. When the user voicecommand is not recognized because of a low signal-to-noise ratio, thetelematics unit advises the user to reduce the ambient noise level. Ifthe user is able to reduce the noise level in the car, for example, byrolling up the vehicle windows, the voice-recognition application mayrecognize the voice command that is repeated after the noise is reduced.If the voice-recognition application is unable to recognize the commandafter several attempts, the speech recognition session ends with anunrecognized-command error. The telematics unit advises the user thatthe voice command was unrecognized. In this case, the user contacts anadvisor to provide the desired service.

It is desirable to adjust the confidence threshold level during a speechrecognition session, if the signal to noise level prevents the spokencommand from being recognized within the default confidence thresholdlevel. It is further desirable to reset to the default confidencethreshold level after the vehicle is turned off.

SUMMARY OF THE INVENTION

One aspect of the present invention provides a method of configuring aspeech recognition unit in a vehicle. The method includes receiving anoise error from the speech recognition unit responsive to a user voicecommand and reducing a confidence threshold for an appropriate grammarset responsive to the received noise error.

Another aspect of the present invention provides a system forconfiguring a speech recognition unit in a vehicle. The system includesmeans for receiving a noise error from the speech recognition unitresponsive to a user voice command and means for reducing a confidencethreshold for an appropriate grammar set responsive to the receivednoise error.

A third aspect of the present invention provides a computer readablemedium storing a computer program which includes computer readable codefor receiving a noise error from the speech recognition unit responsiveto a user voice command and for reducing a confidence threshold for anappropriate grammar set responsive to the received noise error.

The foregoing and other features and advantages of the invention willbecome further apparent from the following detailed description of thepresently preferred embodiment, read in conjunction with theaccompanying drawings. The detailed description and drawings are merelyillustrative of the invention rather than limiting, the scope of theinvention being defined by the appended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention are illustrated by theaccompanying figures, wherein:

FIG. 1 is a schematic diagram of a system for providing access to atelematics system in a mobile vehicle;

FIG. 2 illustrates a flowchart representative of a first embodiment of amethod of configuring a speech recognition unit in a vehicle inaccordance with the present invention;

FIG. 3 illustrates a flowchart representative of a first embodiment of amethod of reducing a confidence threshold in accordance with the presentinvention;

FIG. 4 illustrates a flowchart representative of a second embodiment ofa method of configuring a speech recognition unit in a vehicle inaccordance with the present invention; and

FIG. 5 illustrates a flowchart representative of a third embodiment of amethod of configuring a speech recognition unit in a vehicle inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 illustrates one embodiment of system for data transmission over awireless communication system, in accordance with the present inventionat 100. Mobile vehicle communication system (MVCS) 100 includes a mobilevehicle communication unit (MVCU) 110, a vehicle communication network112, a telematics unit 120, one or more wireless carrier systems 140,one or more communication networks 142, one or more land networks 144,one or more client, personal or user computers 150, one or moreweb-hosting portals 160, and one or more call centers 170. In oneembodiment, MVCU 110 is implemented as a mobile vehicle equipped withsuitable hardware and software for transmitting and receiving voice anddata communications. MVCS 100 may include additional components notrelevant to the present discussion. Mobile vehicle communication systemsand telematics units are known in the art.

MVCU 110 may also be referred to as a mobile vehicle throughout thediscussion below. In operation, MVCU 110 may be implemented as a motorvehicle, a marine vehicle, or as an aircraft. MVCU 110 may includeadditional components not relevant to the present discussion.

Vehicle communication network 112 sends signals to various units ofequipment and systems (detailed below) within MVCU 110 to performvarious functions such as unlocking a door, opening the trunk, settingpersonal comfort settings, and calling from telematics unit 120. Infacilitating interactions among the various communication and electronicmodules, vehicle communication network 112 utilizes network interfacessuch as controller-area network (CAN), International Organization forStandardization (ISO) Standard 9141, ISO Standard 11898 for high-speedapplications, ISO Standard 11519 for lower speed applications, andSociety of Automotive Engineers (SAE) Standard J1850 for high-speed andlower speed applications.

MVCU 110, via telematics unit 120, sends and receives radiotransmissions from wireless carrier system 140. Wireless carrier system140 is implemented as any suitable system for transmitting a signal fromMVCU 110 to communication network 142.

Telematics unit 120 includes a processor 122 connected to a wirelessmodem 124, a global positioning system (GPS) unit 126, an in-vehiclememory 128, a microphone 130, one or more speakers 132, and an embeddedor in-vehicle mobile phone 134. In other embodiments, telematics unit120 may be implemented without one or more of the above listedcomponents, such as, for example GPS unit 126 or speakers 132.Telematics unit 120 may include additional components not relevant tothe present discussion.

In one embodiment, processor 122 is a digital signal processor (DSP).Processor 122 is implemented as a microcontroller, microprocessor,controller, host processor, or vehicle communications processor. In anexample, processor 122 is implemented as an application specificintegrated circuit (ASIC). In another embodiment, processor 122 isimplemented as a processor working in conjunction with a centralprocessing unit (CPU) performing the function of a general purposeprocessor. GPS unit 126 provides longitude and latitude coordinates ofthe vehicle responsive to a GPS broadcast signal received from one ormore GPS satellite broadcast systems (not shown). In-vehicle mobilephone 134 is a cellular-type phone, such as, for example an analog,digital, dual-mode, dual-band, multi-mode or multi-band cellular phone.

Processor 122 executes various computer programs that controlprogramming and operational modes of electronic and mechanical systemswithin MVCU 110. Processor 122 controls communications (e.g. callsignals) between telematics unit 120, wireless carrier system 140, andcall center 170. Processor 122 generates and accepts digital signalstransmitted between telematics unit 120 and a vehicle communicationnetwork 112 that is connected to various electronic modules in thevehicle. In one embodiment, these digital signals activate theprogramming mode and operation modes, as well as provide for datatransfers.

A voice-recognition application is installed in a speech recognitionunit 136. Human voice input through microphone 130 is translated intodigital signals by processor 122. The speech recognition unit 136recognizes the translated digital signals to be words or phrases, whichrepresent commands or words in a grammar set related to the command.Instructions associated with the recognized words are transmitted fromthe speech recognition unit 136 to the processor 122, which activatesthe instructions. In one embodiment, the speech recognition unit 136 isinternal to the processor 122.

Communication network 142 includes services from one or more mobiletelephone switching offices and wireless networks. Communication network142 connects wireless carrier system 140 to land network 144.Communication network 142 is implemented as any suitable system orcollection of systems for connecting wireless carrier system 140 to MVCU110 and land network 144.

Land network 144 connects communication network 142 to client computer150, web-hosting portal 160, and call center 170. In one embodiment,land network 144 is a public-switched telephone network (PSTN). Inanother embodiment, land network 144 is implemented as an Internetprotocol (IP) network. In other embodiments, land network 144 isimplemented as a wired network, an optical network, a fiber network,other wireless networks, or any combination thereof. Land network 144 isconnected to one or more landline telephones. Communication network 142and land network 144 connect wireless carrier system 140 to web-hostingportal 160 and call center 170.

Client, personal or user computer 150 includes a computer usable mediumto execute Internet browser and Internet-access computer programs forsending and receiving data over land network 144 and optionally, wiredor wireless communication networks 142 to web-hosting portal 160.Personal or client computer 150 sends user preferences to web-hostingportal through a web-page interface using communication standards suchas hypertext transport protocol (HTTP), and transport-control protocoland Internet protocol (TCP/IP). In one embodiment, the data includesdirectives to change certain programming and operational modes ofelectronic and mechanical systems within MVCU 110. In operation, aclient utilizes computer 150 to initiate setting or re-setting ofuser-preferences for MVCU 110. User-preference data from client-sidesoftware is transmitted to server-side software of web-hosting portal160. User-preference data is stored at web-hosting portal 160.

Web-hosting portal 160 includes one or more data modems 162, one or moreweb servers 164, one or more databases 166, and a network system 168.Web-hosting portal 160 is connected directly by wire to call center 170,or connected by phone lines to land network 144, which is connected tocall center 170. In an example, web-hosting portal 160 is connected tocall center 170 utilizing an IP network. In this example, bothcomponents, web-hosting portal 160 and call center 170, are connected toland network 144 utilizing the IP network. In another example,web-hosting portal 160 is connected to land network 144 by one or moredata modems 162. Land network 144 sends digital data to and from modem162, data that is then transferred to web server 164. Modem 162 mayreside inside web server 164. Land network 144 transmits datacommunications between web-hosting portal 160 and call center 170.

Web server 164 receives user-preference data from user computer 150 vialand network 144. In alternative embodiments, computer 150 includes awireless modem to send data to web-hosting portal 160 through a wirelesscommunication network 142 and a land network 144. Data is received byland network 144 and sent to one or more web servers 164. In oneembodiment, web server 164 is implemented as any suitable hardware andsoftware capable of providing web services to help change and transmitpersonal preference settings from a client at computer 150 to telematicsunit 120 in MVCU 110. Web server 164 sends to or receives from one ormore databases 166 data transmissions via network system 168. Web server164 includes computer applications and files for managing and storingpersonalization settings supplied by the client, such as doorlock/unlock behavior, radio station preset selections, climate controls,custom button configurations and theft alarm settings. For each client,the web server potentially stores hundreds of preferences for wirelessvehicle communication, networking, maintenance and diagnostic servicesfor a mobile vehicle.

In one embodiment, one or more web servers 164 are networked via networksystem 168 to distribute user-preference data among its networkcomponents such as database 166. In an example, database 166 is a partof or a separate computer from web server 164. Web server 164 sends datatransmissions with user preferences to call center 170 through landnetwork 144.

Call center 170 is a location where many calls are received and servicedat the same time, or where many calls are sent at the same time. In oneembodiment, the call center is a telematics call center, facilitatingcommunications to and from telematics unit 120 in MVCU 110. In anexample, the call center is a voice call center, providing verbalcommunications between an advisor in the call center and a subscriber ina mobile vehicle. In another example, the call center contains each ofthese functions. In other embodiments, call center 170 and web-hostingportal 160 are located in the same or different facilities.

Call center 170 contains one or more voice and data switches 172, one ormore communication services managers 174, one or more communicationservices databases 176, one or more communication services advisors 178,and one or more network systems 180.

Switch 172 of call center 170 connects to land network 144. Switch 172transmits voice or data transmissions from call center 170, and receivesvoice or data transmissions from telematics unit 120 in MVCU 110 throughwireless carrier system 140, communication network 142, and land network144. Switch 172 receives data transmissions from and sends datatransmissions to one or more web-hosting portals 160. Switch 172receives data transmissions from or sends data transmissions to one ormore communication services managers 174 via one or more network systems180.

Communication services manager 174 is any suitable hardware and softwarecapable of providing requested communication services to telematics unit120 in MVCU 110. Communication services manager 174 sends to or receivesfrom one or more communication services databases 176 data transmissionsvia network system 180. Communication services manager 174 sends to orreceives from one or more communication services advisors 178 datatransmissions via network system 180. Communication services database176 sends to or receives from communication services advisor 178 datatransmissions via network system 180. Communication services advisor 178receives from or sends to switch 172 voice or data transmissions.

Communication services manager 174 provides one or more of a variety ofservices, including enrollment services, navigation assistance,directory assistance, roadside assistance, business or residentialassistance, information services assistance, emergency assistance, andcommunications assistance. Communication services manager 174 receivesservice-preference requests for a variety of services from the clientvia computer 150, web-hosting portal 160, and land network 144.Communication services manager 174 transmits user-preference and otherdata to telematics unit 120 in MVCU 110 through wireless carrier system140, communication network 142, land network 144, voice and data switch172, and network system 180. Communication services manager 174 storesor retrieves data and information from communication services database176. Communication services manager 174 may provide requestedinformation to communication services advisor 178.

In one embodiment, communication services advisor 178 is implemented asa real advisor. In an example, a real advisor is a human being in verbalcommunication with a user or subscriber (e.g. a client) in MVCU 110 viatelematics unit 120. In another embodiment, communication servicesadvisor 178 is implemented as a virtual advisor. In an example, avirtual advisor is implemented as a synthesized voice interfaceresponding to requests from telematics unit 120 in MVCU 110.

Communication services advisor 178 provides services to telematics unit120 in MVCU 110. Services provided by communication services advisor 178include enrollment services, navigation assistance, real-time trafficadvisories, directory assistance, roadside assistance, business orresidential assistance, information services assistance, emergencyassistance, and communications assistance. Communication servicesadvisor 178 communicate with telematics unit 120 in MVCU 110 throughwireless carrier system 140, communication network 142, and land network144 using voice transmissions, or through communication services manager174 and switch 172 using data transmissions. Switch 172 selects betweenvoice transmissions and data transmissions.

FIG. 2 illustrates a flowchart 200 representative of a first embodimentof a method of configuring a speech recognition unit 136 in a MVCU 110in accordance with the present invention. During stage S202, thetelematics unit 120 receives a noise error (NE) from the speechrecognition unit 136 responsive to an unrecognized user voice command.The user voice command received by microphone 130 is translated intodigital signals by processor 122. The processor 122 transmits thedigital signal to the speech recognition unit 136. The speechrecognition unit 136 attempts to match the translated digital signalswith digital signals for words stored in the speech recognition unit136.

The digital signals for words stored in the speech recognition unit 136are acoustic models. Grammar sets are associated with commands. Acousticmodels include digital signals for words that are likely to be utteredduring a speech task related to the command. In one embodiment, forexample, a dial-command grammar set includes a representation for theword ‘dial,’ the words for all the numbers from zero to ninety-nine andthe letter ‘O.’

If the speech recognition unit 136 matches the translated digitalsignals with stored digital signals for words, the user voice command isrecognized. If the signal to noise ratio is too low for a match to bemade with a preset confidence threshold, a noise error is generated. Acomputer readable medium storing a computer program within the speechrecognition unit 136 is programmed with computer readable code toattempt to match digital signals, to generate a noise error and totransmit the noise error to the processor 122 in the telematics unit120.

During stage S204, the telematics unit 120 reduces a confidencethreshold (CT) for an appropriate grammar set responsive to the noiseerror (NE) received at the processor 122. A computer readable mediumstoring a computer program within the processor 122 is programmed withcomputer readable code to send a reduce-confidence-threshold instructionto the speech recognition unit 136. The speech recognition unit 136 thenreduces the confidence threshold by a preset amount. The preset amountis stored in the speech recognition unit 136. In one embodiment, thepreset amount is reduced incrementally. For example, the preset amountmay be reduced a predetermined percentage of the range of the confidencethreshold. The predetermined percentage is calculated in response to atleast one factor. Factors include dialect, region, energy levels presentin the spoken utterance, volume, history of spoken utterances by aparticular user.

In some embodiments, the original command is unrecognized by the speechrecognition unit 136 so the confidence level is reduced for all thegrammar sets in the speech recognition unit 136. In another embodiment,the confidence level is reduced for a specific command-grammar-set,which includes all the words and phrases to initiate a command withinthe telematics unit 120. In one embodiment, a specificcommand-grammar-set applies to number grammar for dialing numbers, andconfidence level is reduced for the specific number grammar.

An exemplary method of reducing the confidence threshold for anappropriate grammar set responsive to the received noise error isdescribed below with reference to flowchart 300 in FIG. 3.

During stage S206, the telematics unit 120 announces anunrecognized-command message to a user responsive to the reduction ofthe confidence threshold (CT). The computer readable medium storing acomputer program within the processor 122 is programmed with computerreadable code to generate an advisory message when the instruction toreduce-confidence-threshold is sent to the speech recognition unit 136.The advisory message is a digital signal that is transmitted as spokenwords via speakers 132 so the user is prompted to repeat the voicecommand. In one embodiment, the advisory message indicates the source ofreduced confidence, such as “too much noise.”

The speech recognition unit 136 now has a higher probability ofrecognizing the user voice command since the confidence threshold islower. In one embodiment, given the reduced confidence threshold, thespeech recognition unit 136 will now find more than one possible matchto the repeated user voice command. In this case, the telematics unit120 prompts the user to determine which voice command the user actuallystated. For example, the telematics unit 120 announces, “Did you sayCall Mom?” If the user did not say “Call Mom,” the user says, “No.” Thenthe telematics unit 120 announces, “Did you say Call Tom?” and the usersays, “Yes.” The telematics unit 120 then initiates a call to Tom inaccordance with the user voice command.

During stage S208, the telematics unit 120 resets the confidencethresholds (CTs) to default when ignition is cycled, that is, when theMVCU 110 is turned off. The computer readable medium storing a computerprogram within the processor 122 is programmed with computer readablecode to send a set-confidence-threshold-to-default instruction to thespeech recognition unit 136 when the MVCU 110 is turned off. The defaultconfidence threshold is the confidence threshold that was installed inthe telematics unit 120 at the factory. In one embodiment, the processor122 sends a set-confidence-threshold-to-default instruction to thespeech recognition unit 136 when the MVCU 110 is turned off and on. Inother embodiments, the confidence threshold is stored in the processor122, which is programmed to set the confidence threshold to the defaultlevel when the MVCU 110 is turned off and/or on. In another embodiment,the confidence threshold is set by an advisor at a call center. Inanother embodiment, the confidence threshold is set by a dealer.

FIG. 3 illustrates a flowchart 300 representative of a first embodimentof a method of reducing a confidence threshold in accordance with thepresent invention. During stage S302, the telematics unit 120 retrievesthe current confidence threshold (CT) responsive to a received noiseerror. The computer readable medium storing a computer program withinthe processor 122 is programmed with computer readable code to retrievethe current confidence threshold from a memory (not shown) in the speechrecognition unit 136 when a noise error is received at the telematicsunit 120. In another embodiment, the current confidence threshold isretrieved from the in-vehicle memory 128 in the telematics unit 120.

During stage S304, the telematics unit 120 determines whether thecurrent confidence threshold (CT) equals a minimum confidence threshold(CT). The computer readable medium storing a computer program within theprocessor 122 is programmed with computer readable code to compare theretrieved current confidence threshold with a minimum confidencethreshold to determine if they are equal. The minimum confidencethreshold is stored in the telematics unit 120. In one embodiment, theminimum confidence threshold is stored in the in-vehicle memory 128 inthe telematics unit 120.

In another embodiment, the speech recognition unit 136 compares thecurrent confidence threshold stored in the speech recognition unit 136with a minimum confidence threshold. In this embodiment, the minimumconfidence threshold is stored in a memory (not shown) in the speechrecognition unit 136.

During stage S306, the telematics unit 120 reduces the currentconfidence threshold (CT) by a preset amount based on the determinationmade during stage S304. If the current confidence threshold does notequal the minimum confidence threshold, the computer readable mediumstoring a computer program within the processor 122 is programmed withcomputer readable code to send a reduce-confidence-threshold instructionto the speech recognition unit 136. The speech recognition unit 136contains computer readable code to subtract the preset amount from thecurrent confidence threshold in response to the instruction to reducethe confidence threshold. The preset amount is stored in a memory (notshown) within the speech recognition unit 136. Then the speechrecognition unit 136 uses the reduced confidence threshold in theprocess of recognizing the next user voice command received by thetelematics unit 120, as described above with reference to stage S202 inflowchart 200 in FIG. 2.

In one embodiment, the processor 122 retrieves the preset amount fromin-vehicle memory 128 and sends a reduce-confidence-thresholdinstruction along with the retrieved preset amount, to the speechrecognition unit 136. In another embodiment, the processor 122 subtractsthe preset amount from the current confidence threshold and transmitsthe reduced confidence threshold to the speech recognition unit 136. Inone embodiment, the preset amount, by which the confidence threshold isreduced, is a percentage of the current confidence threshold.

If the current confidence threshold equals the minimum confidencethreshold, the current confidence threshold is not reduced. In thatcase, the telematics unit 120 announces an unrecognized command messageto the user.

FIG. 4 illustrates a flowchart 400 representative of a second embodimentof a method of configuring a speech recognition unit 136 in an MVCU 110in accordance with the present invention. Flowchart 400 describes anembodiment in which the confidence threshold is reduced after announcingmore than one noise reduction advisory messages to the user during aspeech recognition session. In this embodiment, the confidence thresholdis reduced by the preset amount two times responsive to at least tworespective received noise errors. The user is prompted to repeat thevoice-command after each reduction in confidence threshold.

During stage S402, the telematics unit 120 receives a first noise error(NE) from the speech recognition unit (SRU) 136 responsive to a uservoice command not being recognized. During stage S404, the telematicsunit 120 announces a noise reduction advisory message to a userresponsive to the received noise error (NE) to prompt the user to repeatthe voice command. The noise reduction advisory message asks the user toreduce the noise level in the MVCU 110, prior to repeating the voicecommand. In some embodiments, the user is able to reduce some ambientnoise in the MVCU 110. In other embodiments, the noise is external tothe MVCU 110 and the user cannot reduce the noise level in the MVCU 110.The user repeats the voice command. The speech recognition unit 136attempts to recognize the user voice command. If the user voice commandis not recognized, the speech recognition unit 136 transmits a secondnoise error to the telematics unit 120.

During stage S406, the telematics unit 120 receives a second noise error(NE) from the speech recognition unit (SRU) 136 responsive to therepeated user voice command not being recognized by the speechrecognition unit 136. During stage S408, the telematics unit 120announces the noise reduction advisory message to the user responsive tothe second received noise error (NE) to prompt the user to repeat thevoice command for a third time. The user announces the voice command forthe third time. The speech recognition unit 136 attempts to recognizethe third user voice command. If the third user voice command is notrecognized, the speech recognition transmits a third noise error to thetelematics unit 120.

If the third announced user voice command is recognized, the telematicsunit 120 provides the requested service. In this case, the speechrecognition unit 136 transmits an instruction associated with therecognized command to the telematics unit 120 or continues the dialog.

During stage S410, the telematics unit 120 receives the third noiseerror (NE) from the speech recognition unit (SRU) 136 responsive to thethird user voice command not being recognized. During stage S412, thetelematics unit 120 reduces a current confidence threshold (CT) for anappropriate grammar set responsive to the third received noise errorreceived during stage S410. The method of reducing a confidencethreshold proceeds as described above with reference to flowchart 300 inFIG. 3.

During stage S414, the telematics unit 120 announces theunrecognized-command message to the user responsive to the reduction ofthe confidence threshold (CT). The unrecognized-command message promptsthe user to announce the voice command for the fourth time. The userannounces the voice command for the fourth time. The speech recognitionunit 136 attempts to recognize the fourth user voice command. If thefourth user voice command is not recognized, the speech recognitiontransmits a fourth noise error to the telematics unit 120. If the fourthuser voice command is recognized, the telematics unit 120 provides therequested service.

During stage S416, the telematics unit 120 receives a fourth noise error(NE) from the speech recognition unit (SRU) 136 responsive to the fourthuser voice command not being recognized. During stage S418, thetelematics unit 120 reduces the confidence threshold (CT) for theappropriate grammar set responsive to the fourth received noise error(NE). During stage S420, the telematics unit 120 announces an advisorymessage to a user responsive to the second reduction of the confidencethreshold. The advisory message prompts the user to announce the voicecommand for the fifth time.

The flow can proceed in like manner with the telematics unit 120 goingthrough cycles of receiving user voice commands, attempting to recognizethe user voice commands, receiving noise errors, reducing the confidencethreshold and prompting the user to repeat the voice command until oneof three events occur.

The first event to stop the cycle occurs when the speech recognitionunit 136 recognizes the user voice command and the telematics unit 120provides the requested service. The second event to stop the cycleoccurs when the minimum confidence threshold is reached before thespeech recognition session recognized the user voice command. The thirdevent to stop the cycle occurs when the recognition is not successfulafter a predetermined number of attempts, such as 5. In this case, thetelematics unit 120 announces a message to the user that the speechrecognition session is terminated. In one embodiment, the telematicsunit 120 announces, “The command is not recognized. Please try again.”

FIG. 5 illustrates a flowchart 500 representative of a third embodimentof a method of configuring a speech recognition unit 136 in a MVCU 110in accordance with the present invention. In this embodiment, unlike thesecond embodiment described with reference to flowchart 400 in FIG. 4,the user is only prompted to repeat the message once. The flowchart 500begins at a point that follows the stages of S402 and S404 in flowchart400 in FIG. 4.

During stage S502, the telematics unit (TU) 120 receives a repeated uservoice command. During stage S504, the telematics unit 120 receives asecond noise error (NE) from the speech recognition unit 136 responsiveto the repeated user voice command not being recognized by the speechrecognition unit 136. During stage S506, the repeated user voice commandis stored in the telematics unit (TU) 120. The repeated user voicecommand is received by microphone 130 and translated into digitalsignals by processor 122. In one embodiment, the digital signals of therepeated user voice command are temporarily stored in a memory (notshown) in the speech recognition unit 136. In another embodiment, thedigital signals of the repeated user voice command are temporarilystored in the in-vehicle memory 128 in the telematics unit 120. Thedigital signals of the repeated user voice command are deleted frommemory when the speech recognition session is terminated.

During stage S508, the confidence threshold (CT) is reduced for anappropriate grammar set responsive to the second received noise error(NE), as described above with reference to flowchart 300 in FIG. 3.During stage S510, the speech recognition unit 136 attempts to recognizethe stored repeated user voice command after the confidence threshold isreduced. The speech recognition unit 136 retrieves the temporarilystored digital commands of the repeated user voice command and attemptsto match them with digital commands in the appropriate grammar set. Thedigital signals in the appropriate grammar set are stored in the speechrecognition unit 136. If the reduced confidence threshold is still toohigh for a match, a third noise error is generated by the speechrecognition unit 136 and transmitted to the processor 122.

During stage S512, the telematics unit 120 determines if a noise error(NE) was received responsive to the attempt by the speech recognitionunit 136 to recognize the stored user voice command. If a noise errorwas not received, the telematics unit (TU) 120 provides the requestedservice during stage S520. During stage S520, the speech recognitionunit 136 transmits an instruction associated with the recognized commandto the telematics unit 120 or continues with the dialog. The telematicsunit 120 receives the associated instruction and initiates the processor processes appropriate to respond to the user voice command.

If a noise error was received during stage S512, the telematics unit 120determines if the current confidence threshold (CT) equals the minimumconfidence threshold (CT) during stage S514. If the current confidencethreshold equals the minimum confidence threshold, then during stageS522, the telematics unit (TU) 120 announces an advisory message to theuser. In this case, the telematics unit 120 announces a message to theuser that the speech recognition session is terminated. In oneembodiment, the telematics unit 120 announces, “Command not recognized.Please try again.”

If the current confidence threshold is greater than the minimumconfidence threshold, then during stage S516, the telematics unit (TU)120 reduces the confidence threshold (CT) for the appropriate grammarset responsive to the received noise error (NE) as described above inreference to stage S306 in flowchart 300 in FIG. 3.

During stage S518, the speech recognition unit 136 attempts to recognizethe stored repeated voice command as described above in stage S510. Thenthe flow returns to stage S512.

Until one of three events occurs, the flowchart 500 cycles throughstages S512-S518 without prompting the user to repeat the voice command.The first event to stop the cycle through stages S512-S518 occurs whenthe speech recognition unit 136 recognizes the user voice command andthe telematics unit 120 provides the requested service as describedabove with reference to stage S520. The second event to stop the cyclethrough stages S512-S518 occurs when the minimum confidence threshold isreached and the telematics unit 120 announces an unrecognized command tothe user as in stage S522. The third events occur after the recognitionwas not successful.

While the embodiments, of the invention disclosed herein are presentlyconsidered to be preferred, various changes and modifications can bemade without departing from the spirit and scope of the invention. Thescope of the invention is indicated in the appended claims, and allchanges that come within the meaning and range of equivalents areintended to be embraced therein.

1. A method of configuring a speech recognition unit in a vehicle, themethod comprising: receiving a noise error from the speech recognitionunit responsive to a user voice command; and reducing a confidencethreshold for an appropriate grammar set responsive to the receivednoise error.
 2. The method of claim 1, further comprising: announcing anadvisory message to a user responsive to the reduction of the confidencethreshold.
 3. The method of claim 1, wherein reducing a confidencethreshold comprises: retrieving a current confidence thresholdresponsive to the received noise error; determining whether the currentconfidence equals a minimum confidence threshold; and reducing thecurrent confidence threshold by a preset amount based on thedetermination.
 4. The method of claim 3, wherein the confidencethreshold is reduced by the preset amount two or more times responsiveto at least two or more respective received noise errors.
 5. The methodof claim 4, wherein the confidence threshold is reduced by the presetamount until the current confidence threshold equals the minimumconfidence threshold.
 6. The method of claim 1, further comprising:resetting the confidence thresholds to default when ignition is cycled.7. The method of claim 1, further comprising: announcing a noisereduction advisory message to a user responsive to the received noiseerror; and receiving a second noise error from the speech recognitionunit responsive to a repeated user voice command, wherein the repeateduser voice command is announced responsive to the noise reductionadvisory message, and wherein the reducing a confidence threshold for anappropriate grammar set is responsive to the received second noiseerror.
 8. The method of claim 7, wherein reducing a confidence thresholdis responsive to announcing more than one noise reduction advisorymessages during a speech recognition session.
 9. The method of claim 7,further comprising: storing the repeated user voice command in thetelematics unit; and attempting to recognize the stored repeated uservoice command at the speech recognition unit after the confidencethreshold is reduced.
 10. The method of claim 9, further comprising:reducing a confidence threshold for the appropriate grammar setresponsive to a third received noise error, wherein the third receivednoise error is responsive to the attempting to recognize the stored uservoice command; and attempting to recognize the stored repeated uservoice command at the speech recognition unit after the confidencethreshold is reduced twice.
 11. A system for configuring a speechrecognition unit in a vehicle, the system comprising: means forreceiving a noise error from the speech recognition unit responsive to auser voice command; and means for reducing a confidence threshold for anappropriate grammar set responsive to the received noise error.
 12. Thesystem of claim 11, further comprising: means for announcing an advisorymessage to a user responsive to the reduction of the confidencethreshold.
 13. The system of claim 11, wherein the means for reducing aconfidence threshold comprise: means for retrieving a current confidencethreshold responsive to the received noise error; means for determiningwhether the current confidence equals a minimum confidence threshold;and means for reducing the current confidence threshold by a presetamount based on the determination.
 14. The system of claim 7, furthercomprising: means for storing a repeated user voice command in thetelematics unit; and means for attempting to recognize the storedrepeated user voice command at the speech recognition unit after theconfidence threshold is reduced.
 15. The system of claim 11, furthercomprising: means for resetting the confidence thresholds to defaultwhen ignition is cycled.
 16. A computer readable medium storing acomputer program comprising: computer readable code for receiving anoise error from the speech recognition unit responsive to a user voicecommand; and computer readable code for reducing a confidence thresholdfor an appropriate grammar set responsive to the received noise error.17. The medium of claim 16, further comprising: computer readable codefor announcing an advisory message to a user responsive to the reductionof the confidence threshold.
 18. The medium of claim 16, whereincomputer readable code for reducing a confidence threshold comprises:computer readable code for retrieving a current confidence thresholdresponsive to the received noise error; computer readable code fordetermining whether the current confidence equals a minimum confidencethreshold; and computer readable code for reducing the currentconfidence threshold by a preset amount based on the determination. 19.The medium of claim 16, further comprising: computer readable code forresetting the confidence thresholds to default when ignition is cycled.20. The medium of claim 16, further comprising: computer readable codefor storing a repeated user voice command in the telematics unit; andcomputer readable code for attempting to recognize the stored repeateduser voice command at the speech recognition unit after the confidencethreshold is reduced.